Fuse trimming circuits are employed for improving the output accuracy of an internal circuit in a semiconductor integrated circuit (IC) (refer to Patent Document 1, for example). A description will be directed to a conventional fuse trimming circuit, with reference to FIG. 5. A fuse trimming circuit 10 includes a CMOS input circuit 11, a fuse resistor 12, a trimming pad 13, a P-channel MOS transistor 14, and N-channel MOS transistors 15 and 16 for static protection. The fuse resistor 12 can be blown by application of a voltage or a current and pulls down a level at the input terminal of the CMOS input circuit 11 to a ground potential GND in an unblown state. The voltage or the current for blowing the fuse resistor 12 is supplied to the trimming pad 13. The P-channel MOS transistor 14 pulls up the level at the input terminal of the CMOS input circuit 11 to a power supply potential VDD in a state where the fuse resistor 12 is blown.
One end of the fuse resistor 12 is connected to the input terminal of the CMOS input circuit 11, and the other end of the fuse resistor 12 is connected to a ground line GND. The trimming pad 13 is connected to the one end of the fuse resistor 12. The source of the MOS transistor 14 is connected to a power supply line VDD. The drain of the MOS transistor 14 is connected to the input terminal of the CMOS input circuit 11. The gate of the MOS transistor 14 is connected to the ground line GND. The drain of the MOS transistor 15 is connected to the power supply line VDD. The source of the MOS transistor 15 is connected to the input terminal of the CMOS input terminal 11. The gate of the MOS transistor 15 is connected to the ground line GND. The drain of the MOS transistor 16 is connected to the input terminal of the CMOS input circuit 11. The source and gate of the MOS transistor 16 are connected to the ground line GND.
When trimming is unnecessary in the fuse trimming circuit 10, the fuse resistor 12 is not blown. Thus, the input terminal of the CMOS input circuit 11 is fixed at an “L” level (the GND potential). When the trimming is necessary, the predetermined voltage or current is supplied to the trimming pad 13, thereby blowing the fuse resistor 12. Thus, the input terminal of the CMOS input circuit 11 is fixed at an “H” level (the VDD potential).
[Patent Document 1]
JP Patent Kokai Publication No. JP-P2000-133778A (FIG. 2)